if you are planning on doing sigils wait till you get into a realm and find 2-3 buffs for your team or debuffs for the enemies in that realm. these buffs and debuffs are carried into battles agianst sigil teams and will make them a lot easier to beat

nature mages:
hybridization costs 50 perk points but if you get it you basically get 60% more defense,speed,and,health and this will make taking on sigils and the rest of the game a lot easier. (note if your are using a pure hunter or pure familar team this wont do anything for you)
i dont know how the lone wolf perk works but its probably really nice if you are using a team where you have summon spells that activate on the start of battle.
other mages:
get perks and then build around them. dont know why nature mages get off so easy with good perks that work with any setup but everyone else gets stuff that makes them use class based builds

if your team is too heavy on certian strats you might get owned really bad if the randomly generated team thats thrown agianst you counters a lot of your strats

if you have a magic oritended team and the sigil starts your team off with silence than just dont do that sigil.
if you have a team that relies a lot on dying and reviving constantly dont challenge a sigil that doesnt allow you to resurrect.

sigils level and gene level are based on your teams highest gene level and highest level so have a team compistion with close together gene level and normal level for the easiest time to beat a sigil

sigils difficultly is based on creature level and gene strength, so it is best to use a team of no gene stregenth and equally leveled creatures.(major strat)
if you use new game+ one of the options turns gene stregnth off entirely making it so there is no increase in gene stregenth on sigils(boring strat)